JP2004307877A - Molecular beam source for depositing thin film, and thin-film depositing method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which forms a film having high thickness uniformity over a wide area on the surface to be film-formed of a substrate while obtaining a high film-forming efficiency, causes no unintentional leakage of steam from a crucible, and facilitates a control for film formation. <P>SOLUTION: A molecular beam source for depositing a thin film comprises a crucible 1 for accommodating a film-forming material 10, a heating means for sublimating or vaporizing a film-forming material 10 in the crucible 1 by heating, a pressure-buffering chamber 2 which is a space for introducing molecules produced in the crucible 1 from the film forming material 10 through a first valve 9, and is connected to the crucible 1 through the first valve 9, a molecule-emitting hole 7 with a long slit shape for emitting the molecules of the film-forming material toward a substrate (s) to be film-formed from the pressure-buffering chamber 2, and a second valve 8 for adjusting the opened area of the molecule-emitting hole 7. The film-depositing method includes forming a film while making the opened area of the second valve 8 smaller than the opened area of the first valve 9, and relatively moving the molecule-emitting hole 7 and the substrate (s) in a direction perpendicular to the longitudinal direction of the molecule ejection port 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, by heating a film-forming material, the film-forming material is sublimated or melted and evaporated to generate molecules of the film-forming material, and the molecules of the film-forming material are emitted toward a solid surface. The present invention relates to a thin film deposition molecular beam source cell used for growing a film by depositing molecules on a solid surface, and a thin film deposition method using the same.
[0002]
[Prior art]
A thin film deposition apparatus called a molecular beam epitaxy apparatus installs a substrate in a vacuum chamber capable of reducing the pressure to a high vacuum, heats the substrate to a required temperature, and moves a molecule such as a Knudsen cell toward a thin film growth surface of the substrate. A source cell is installed. The film-forming material stored in the crucible of the molecular beam source cell is heated by a heater to sublimate or melt and evaporate, and the generated molecules are incident on the thin film growth surface of the substrate, and the thin film is epitaxially grown on the surface. Then, a film of a film forming material is formed.
[0003]
The molecular beam source cell used in such a thin film deposition apparatus stores a film forming material in a crucible made of, for example, PBN (pyrrolytic boron nitride) having high thermal and chemical stability. Then, the film-forming material is heated by an electric heater provided outside the crucible, thereby sublimating or melting and evaporating the film-forming material to generate film-forming molecules.
[0004]
2. Description of the Related Art In recent years, research and development of organic electroluminescent elements (organic EL elements) have been promoted in fields such as displays and optical communications. This organic EL element is an element in which a light emitting layer is formed of an organic low molecular weight or organic high molecular weight material having EL light emitting ability, and its characteristics are attracting attention as a self-luminous type element. For example, the basic structure is such that a film of a hole transporting material such as triphenyldiamine (TPD) is formed on a hole injecting electrode, and a fluorescent substance such as an aluminum quinolinol complex (Alq ₃ ) is laminated thereon as a light emitting layer. Further, a metal electrode having a small work function, such as Mg, Li, or Ca, is formed as an electron injection electrode.
[0005]
[Problems to be solved by the invention]
Recently, large screens have become a requirement of the times. Therefore, even in the display using the organic EL as described above, it is required to form an organic EL film on a large-sized substrate. In particular, in a display using an organic EL, it is required to form a uniform organic EL film on a substrate.
[0006]
However, as in a conventional vacuum deposition apparatus used for forming an organic EL film, a film forming material is sublimated or evaporated from one crucible to fire molecules on the surface of the substrate, and the film forming material is deposited. In the method of growing a film, it is difficult to form a uniform thin film on a large-area substrate.
[0007]
Further, when such an organic EL material is discharged from the molecule discharge port of the crucible toward the substrate and deposited on the substrate to form a film, if the distance between the molecule discharge port of the crucible and the film-forming surface of the substrate is short, The film thickness of the film-forming material becomes extremely thick at the portion facing the molecular emission port on the film-forming surface of the substrate, and the film thickness suddenly becomes thinner away from the portion facing the molecule emission port. That is, the uniformity of the film thickness is extremely deteriorated. Therefore, the film must be formed with a certain distance between the molecule discharge port of the crucible and the film forming surface of the substrate.
[0008]
However, the farther the molecular emission port of the crucible is separated from the film-forming surface of the substrate, the smaller the amount of the film-forming material actually deposited on the substrate with respect to the consumed film-forming material. There is a problem of getting worse. Since many organic EL materials are expensive, if the yield of film formation, that is, film formation efficiency, is low, this causes a high cost.
Furthermore, since the organic EL material has a high vapor pressure even at a low temperature, unintended vapor leakage from the crucible is likely to occur. For this reason, there is a problem that it is extremely difficult to control the film formation, and it is difficult to form a thin film having a target film quality and thickness.
[0009]
The present invention has been made in view of such problems in the conventional thin film deposition means, and can form a film having high uniformity of film thickness over a wide range on a film formation surface of a substrate while obtaining high film formation efficiency. It is another object of the present invention to provide a molecular beam source for depositing a thin film that does not cause unintended leakage of vapor from a crucible and that can easily control film formation, and a thin film deposition method using the same.
[0010]
[Means for Solving the Problems]
In the present invention, in order to achieve the above object, the molecules of the film forming material 10 evaporated in the crucible 1 are guided directly to the pressure buffer chamber 2 having a certain space without radiating directly to the substrate s, Thus, after the vapor pressure of the film forming material 10 is stably maintained at the equilibrium pressure, the film is discharged from the molecule release port 7 of the pressure buffer chamber 2. Further, the pressure buffer chamber 2 is connected to the crucible 1 via the first valve 9 so that the film-forming material 10 can have a stable equilibrium pressure in the pressure buffer chamber 2. A second valve 8 is provided at the molecule release port 7, the opening area of the second valve 8 is made smaller than that of the first valve 9, and a pressure load can be applied to the pressure buffer chamber 2.
[0011]
That is, the molecular beam source for depositing a thin film according to the present invention comprises a crucible 1 containing a film forming material 10, heating means for heating the film forming material 10 in the crucible 1 to sublimate or evaporate the same, And a pressure buffer chamber 2 which is connected through a first valve 9 to introduce molecules of the film forming material 10 generated in the crucible 1 through the first valve 9. It has a long slit-shaped molecule emission port 7 for emitting molecules of a film forming material toward a substrate s on which a film is to be formed, and a second valve 8 for adjusting the opening area of the molecule emission port 7. .
[0012]
The thin film deposition method according to the present invention for growing a thin film on a solid surface using the molecular beam source for thin film deposition according to the present invention has a smaller opening area of the second valve 8 than an opening area of the first valve 9. Meanwhile, molecules are emitted from the elongated slit-shaped molecule emission port 7 onto the surface of the substrate s, and a film is formed on the surface of the substrate s.
[0013]
In such a molecular beam source for thin film deposition according to the present invention and a thin film deposition method using the same, once the molecules of the film forming material 10 evaporated in the crucible 1 are directly radiated toward the substrate s, a certain degree is reached. It is led to the pressure buffer chamber 2 having a space, where the vapor pressure of the film forming material 10 can be stably maintained at an equilibrium pressure. Thereafter, since the molecules of the film-forming material 10 are released from the molecule release port 7 of the pressure buffer chamber 2, even molecules of the film-forming material having a low vapor pressure and a high vapor pressure can be stably released.
[0014]
In particular, by making the opening area of the second valve 8 smaller than the opening area of the first valve 9, the inside of the pressure buffer chamber (2) can be easily maintained at an equilibrium pressure. Thus, molecules are emitted from the elongated slit-shaped molecule emission port 7 onto the surface of the substrate s and are formed on the surface of the substrate s, so that the molecular pressure in the pressure buffer chamber 2 is stabilized. It can be kept in equilibrium.
[0015]
In addition, the pressure buffer chamber 2 is formed as a long space, and a long slit-shaped molecule discharge port 7 is provided in the longitudinal direction thereof so that the vapor pressure of the film forming material 10 in the pressure buffer chamber 2 is in an equilibrium state. In addition, molecules of the film forming material can be uniformly discharged over the entire length of the molecule discharge port 7 provided in the pressure buffer chamber 2. Therefore, the film is formed while relatively moving the elongated slit-shaped molecule emission port 7 and the substrate s in a direction orthogonal to the longitudinal direction of the molecule emission port 7, thereby covering a wide area on the deposition surface of the substrate s. A thin film having uniform film quality and thickness can be formed.
[0016]
Further, a first valve 9 is provided in front of the pressure buffer chamber 2, and a second valve 8 is provided in a long slit-shaped molecule discharge port 7 of the pressure buffer chamber 2, so that the pressure of the molecules in the crucible 1 is in a predetermined state. When the pressure does not reach or when the pressure buffer chamber 2 does not reach the equilibrium thickness, the first and second valves 9 and 8 are closed to form a film forming material such as an organic EL material having a low vapor pressure even at a low temperature. Even so, unintended release of molecules can be minimized. This facilitates the control of film formation, and a thin film having a desired film thickness and quality can be formed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described specifically and in detail with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional side view showing an embodiment of a thin film forming molecular beam source according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a diagram showing the formation of a thin film on a substrate s by the thin film forming molecular beam source. FIG. 5 is a schematic vertical sectional side view showing a state in which the process is performed.
[0018]
A film forming material 10 is stored in the crucible 1. In this case, in consideration of the evaporation efficiency of the film forming material 10, as disclosed in Japanese Patent Application Laid-Open No. 2003-2778, the film forming material 10 is thermally and chemically stable together with the film forming material 15, and has a higher thermal conductivity than the film forming material 15. A granular heat transfer medium with a high rate is stored. Alternatively, as shown in FIG. 4, a granular heat transfer medium 14 is provided as a core and the surface thereof is coated with a film-forming material 15, and this is stored in the crucible 1.
[0019]
Around the crucible 1, a heater 4 as a heating means is arranged, whereby the film forming material 10 is heated inside the crucible 1, and sublimates or evaporates to generate molecules of the film forming material 10. At this time, the heat transfer medium 14 improves the heat transfer inside the crucible 1 and realizes uniform sublimation or evaporation of the film forming material 10.
[0020]
The upper end of the crucible 1 communicates with the pressure buffer chamber 2 via the molecular passage 3. The molecular passage portion 3 is a cylindrical member rising from the upper end of the crucible 1, and a needle valve is provided as a first valve 9 in the middle thereof. The molecular passage section 3 is opened and closed by opening and closing the first valve, or the opening area thereof is adjusted.
A heater 6 as a heating means is also arranged around the molecule passing portion 3 of the crucible 1, and the molecules of the film forming material in the molecule passing portion 3 are maintained in the state of the molecules.
[0021]
The pressure buffer chamber 2 is a long box having a central lower portion communicating with the upper end of the molecule passage section 3 and has a certain space. At the center of the upper wall of the pressure buffer chamber 2, a long slit-shaped molecule discharge port 7 is opened along the longitudinal direction. A funnel-shaped molecule release guide 12 is provided upward from the periphery of the molecule release port 7.
[0022]
Further, the tip of a long blade-shaped valve element is inserted into the molecule release port 7 to form a second valve 8. By moving the long blade-shaped valve body of the second valve 8 up and down, the long slit-shaped molecule release port 7 is opened and closed at the tip, or the opening area is adjusted. Therefore, the length is the same as the length of the long slit-shaped molecule discharge port 7 of the long blade-shaped valve element.
A heater 5 as a heating means is also arranged around the pressure buffer chamber 2, and the molecules of the film forming material in the pressure buffer chamber 2 are maintained in the state of the molecules.
[0023]
In order to form a thin film on the film formation surface of the substrate s using such a thin film deposition molecular beam source, first, the crucible is heated by the heater 4 with the first valve 9 and the second valve 8 closed. The film-forming material 10 therein is heated from around 1 and sublimated or evaporated to generate molecules of the film-forming material 10. At this time, since the first valve 9 and the second valve 8 are closed, even if the film forming material 10 such as an organic EL material having a relatively low temperature and a high vapor pressure is used, the molecules of the film forming material 10 remain in the crucible 1. Does not leak from When the sublimation or evaporation of the film forming material 10 is continued, equilibrium is reached in the crucible 1 at a pressure corresponding to the temperature of the film forming material 10. Of course, in this state, the molecular passage section 3 is heated by the heater 6.
[0024]
After the pressure inside the crucible 1 reaches the equilibrium pressure in this way, the first valve 9 is opened while the inside of the pressure buffer chamber 2 is heated to a predetermined temperature by the heater 5 and the molecules of the film forming material are subjected to pressure buffering. Introduce into room 2. At this time, by closing the second valve 8, the pressure buffer chamber 2 eventually reaches equilibrium at a pressure corresponding to the temperature of the film forming material 10. In this state, the pressure of the molecules of the film forming material inside the pressure buffer chamber 2 can be made substantially uniform over the entire length.
[0025]
After the inside of the pressure buffer chamber 2 reaches an equilibrium state at a predetermined pressure, the second valve 8 is opened, and molecules of the film forming material are released from the long slit-shaped molecule release port 7. At this time, since the pressure of the molecules of the film-forming material is substantially uniform over the entire length of the pressure buffer chamber 2, a uniform amount of the molecules of the film-forming material is discharged from the molecule discharge port 7 in the longitudinal direction. At this time, by adjusting the opening area of the second valve 8 smaller than the opening area of the first valve 9, the pressure of the molecules of the film forming material in the pressure buffer chamber 2 is stably balanced. , And the pressure of the molecules of the film forming material can be kept substantially uniform over the entire length of the pressure buffer chamber 2.
[0026]
As shown in FIG. 3, the substrate s is installed with its film-forming surface facing downward to the molecule release port 7 of the pressure buffer chamber 2. As a result, molecules of the film-forming material released from the molecule release port 7 of the pressure buffer chamber 2 are released toward the film-forming surface of the substrate s, and the molecules adhere to and deposit on the film-forming surface of the substrate s. A thin film is formed. In this case, the film is formed while relatively moving the molecule release port 7 of the pressure buffer chamber 2 and the film formation surface of the substrate s in a direction perpendicular to the longitudinal direction of the molecule release port 7. The relative movement speed is determined by the amount of molecules of the film-forming material released per unit time from the molecule release port 7 of the pressure buffer chamber 2 and the thickness of the thin film to be formed on the film-forming surface of the substrate s. Determined by the relationship. Since this is a relative movement, one or both of the pressure buffer chamber 2 and the substrate s are moved and their relative positions are changed.
[0027]
The funnel-shaped molecule release guide 12 standing from the periphery of the molecule release port 7 restricts the release direction of the molecule released from the molecule release port 7 and prevents the molecule from spreading. Thereby, the film formation efficiency can be improved.
It is also possible to connect a plurality of crucibles 1 to the pressure buffer chamber 2 in order to increase the productivity of film formation, and to increase the amount of released molecules of the film formation material per unit time to improve the productivity. It is particularly effective for
[0028]
FIG. 5 shows three examples of the structure of the molecule release port 7 of the pressure buffer chamber 2 and the second valve for opening and closing the molecule release port and adjusting the opening area thereof.
5A, as described above, the tip of the blade-shaped valve body 8a is inserted into the molecule release port 7, and the molecule release port 7 is opened and closed with the wedge-shaped tip, or the opening area is adjusted. This is an example. FIG. 5B shows an example in which the plate-shaped valve element 9b is moved up and down by the operation pin 12, thereby opening and closing the molecule release port 7 or adjusting the opening area thereof. FIG. 5C shows an example in which the partially cylindrical valve element 9c is rotated while being in contact with the molecule release port 7, thereby opening and closing the molecule release port 7 or adjusting the opening area thereof.
[0029]
【The invention's effect】
As described above, the molecular beam source for thin film deposition and the thin film deposition method using the same according to the present invention can stably release molecules of a film forming material having a high vapor pressure even at a low temperature. Elongated slit-shaped molecule emission port 7 Since molecules of almost uniform quality and quantity can be emitted over the entire length of the molecule emission port 7, the molecule emission port 7 and the substrate s are relatively positioned in the longitudinal direction of the molecule emission port 7. By forming the film while moving, a thin film having uniform film quality and thickness can be formed over a wide area on the film formation surface of the substrate s. The opening and closing of the first valve 9 and the second valve 8 can minimize unintended release of molecules even when the film is formed of a material such as an organic EL material having a low vapor pressure even at a low temperature. Control becomes easier.
[Brief description of the drawings]
FIG. 1 is a schematic vertical sectional side view showing one embodiment of a molecular beam source for forming a thin film according to the present invention.
FIG. 2 is a plan view showing the same embodiment of the molecular beam source for forming a thin film.
FIG. 3 is a schematic vertical sectional side view showing a state in which a thin film is formed on a substrate by the film-forming molecular beam source according to the embodiment.
FIG. 4 is a cross-sectional view showing an example of a preferable film-forming material to be housed in a crucible when forming a thin film on a substrate by the film-forming molecular beam source according to the embodiment.
FIG. 5 is a partial cross-sectional view showing an example of the structure of a molecular discharge port of a pressure buffer chamber and a second valve for opening and closing the molecular discharge port and adjusting the opening area thereof in the embodiment of the molecular beam source for forming a thin film. .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crucible 2 Pressure buffer room 7 Molecular discharge port of pressure buffer room 8 Second valve 9 First valve 10 Film forming material s Substrate

Claims (5)

In the molecular beam source for vacuum deposition, which heats the film forming material (10) to sublimate or evaporate the film forming material (10) and generate molecules for growing a thin film on a solid surface, A crucible (1) for storing (10), heating means for heating and sublimating or evaporating the film-forming material (10) in the crucible (1), the crucible (1) and a first valve (9); ), And a pressure buffer chamber (2) which is a space for introducing molecules of the film forming material (10) generated in the crucible (1) through the first valve (9); A long slit-shaped molecule emission port (7) for emitting molecules of the film-forming material from the chamber (2) toward the substrate (s) on which a film is to be formed, and a second area for adjusting the opening area of the molecule emission port (7). A molecular beam source cell for depositing a thin film, comprising: a second valve (8). 2. The molecular beam source for depositing a thin film according to claim 1, wherein the pressure buffer chamber (2) is a long space, and has a long slit-shaped molecule emission port (7) provided in a longitudinal direction thereof. . 2. A heating means for heating the inside of the pressure buffer chamber (2) so that the molecules of the film forming material in the pressure buffer chamber (2) can maintain the state of the molecules. 3. The molecular beam source for thin film deposition according to item 2. In a thin film deposition method for heating a film forming material (10) to sublimate or evaporate the film forming material (10) to grow a thin film on a solid surface, a crucible (1) containing a film forming material (10) is used. ) And heating means for heating and sublimating or evaporating the film-forming material (10) in the crucible (1), the crucible (1) being connected to the crucible (1) via a first valve (9), A pressure buffer chamber (2) which is a space for introducing molecules of the film forming material (10) generated in (1) through the first valve (9), and a substrate on which a film is formed from the pressure buffer chamber (2). It has a long slit-shaped molecule release port (7) for releasing molecules of the film forming material toward (s), and a second valve (8) for adjusting the opening area of the molecule release port (7). Using the molecular beam source cell for thin film deposition, the second valve ( ), The molecules are emitted onto the surface of the substrate (s) from the elongated slit-shaped molecule emission port (7) while the opening area is reduced, and a film is formed on the surface of the substrate (s). Thin film deposition method using a molecular beam source for thin film deposition. The film is formed while relatively moving the elongated slit-shaped molecule emission port (7) and the substrate (s) in a direction orthogonal to the longitudinal direction of the molecule emission port (7). A thin film deposition method using a molecular beam source for thin film deposition.

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